Stabilization of polymerizable heterocyclic nitrogen compounds



United States Patent STABILIZATION OF BOIJYMERIZA'BIJE HETERO- CYCLIC NITROGENrCOMPOUNDS- Mack, F. Potts, Paul S. Hudson,v and'Warren L. Smith, 'Bar'tlsville, ()klaz gassignors; to Phillips Petroleum Company; a corporationof Delaware No Drawing. Application May 27, 1952, Serial No; 290,321

This invention relates to the stabilization of I polymerizable-materials- IILOHC 'Of its aspects this invention relates 2 to the stabilization 1 of polymerizable heterocyclic nitrogen compounda-unden storage and handling condi-' tion'sc and during distillation or at elevated temperatures. lnlanother of its aspects this invention'relates to a method for preventing .loss' of heterocyclic nitrogen compounds due to polymerization. v

It' is welI kn'own that unsaturated, polymerizable heterocyclic nitrogen compounds tend to polymerize during storage and various handling conditions, .especially during distillation, and consequently yieldsandrecovery of these compounds are often considerably diminishegl due'to this unwanted'and undesirable polymerization. Also, besides reducing yields andrecovery of these polymerizable heterocyclic nitrogen compounds; often-the polymerized material adversely affects the rea'ctions wherein these polymerizable compounds are employed as reactants; as well asfth'e' products which are derived frorn'these reac- 'tions;

Accordingly, it is an object of this invention to prevent andlor 'inhibit theipolymerization' of polymerizable heterocyclic nitrogencompounds during-storage and other'hanfides which :are applicable in the practice of this invention include, selenium inonosulfide SeS,l selenium disulfide SeSE, aud'tlie various tellu'rium sulfides, especially te'llurium disulfide TeSz. Of course, mixtures of these sulfides may be used.

These sulfides are effective as polymerization inhibitors over a wide range of temperatures, from below and about 40 F. up to and above 400 F. The amount of these polymerization inhibiting sulfides which need be added to inhibit polymerization usually varies with the amount and type of polymerizable heterocyclic nitrogen compound to be inhibited. Often a trace of these sulfides is sufiicient in the presence of a polymerizable heterocyclic nitrogen compound to inhibit the polymerization of these compounds. Usually an amount of sulfide in the range 0.001 to 5.0% by weight, preferably in the range 0.05 to- 1.0% by weight, based on the weight of the polymerizable heterocyclic nitrogen compound is suflicient. Larger amounts of these sulfides, even as high as 10% by weight and higher can be used if desired, although under most circumstances this is not necessary.

These sulfides. are onlIyr slightly soluble-in; th'ei poly== merizable heterocyclic nitrogen-compounds andzas aeresult the. sulfides arerusually present therewith. ini a-finely die videcl'isolidi state; preferably as a: stable: suspension: in th'e nitrogen: baseror'roth'erwisa intimately. and/or homogene ously admixed therewith. A sulfide, such as selenium monosulfide; is generally'added as a fine'powder to the COIIlPOllIldtO be inhibited against polymerization andith'e' mixturezstirred'andiagitatedfto disperse the sulfide therein; If des'iredotxnecessary: the mixture may be'warmed'i in orderrtorbetten disperse and/or. dissolve the sulfide therein.

The recovery of= these: s'ulfidesi'fro'm thel polymerizable heterocyclic nitrogen compoundwith which admixed is relatively simple and easily etfected, After storage, handling orfshipme'nt of the stabilized'heterocyclic nitrogen compound, the compound can be easily and readily sep-- arated and recovered from the polymerization-inhibiting sulfide: either by distillation, preferably under a reduced pressure, or'by any other convenient manner such'as by filtration; settling, decanting, etc.

The polymerizable heterocyclic nitrogen compounds which are inhibited against polymerization by seleniumand tellurium sulfides in accordance with this invention include the polymerizable heterocyclic nitrogen compounds of thepyridine and quinoline (including i'soquinoline) series,-especially the nuclear (ring) alkyl'substitutedderivatives thereof. These polymerizable heterocyclic nitrogen compounds include the" substituted'nitrogen compounds wherein R is a hydrogen atom or a hydrocarbyl (containing only carbon and hydrogen atoms) radical, preferably'having nofmore'thaii 12 carbon'atoms. The vinyl substituted compounds;-,es peciallythose containing only one substituentvinyl group, as well as the nuclear alkyl substituted derivatives thereof are particularly applicable in' th'epractice of this inventiona ltiis 'preferredhowever, that the total nurnbercof carbonatoms in the nuclear (ring) substituted alkyl groupor groups be notmore than twelve. In addition to the vinyl substituted heterocyclic nitrogen compounds the isopropenyl substituted compounds (i. e; a vinyl group having amethyl substituent in the alpha position) can also be inhibited. Typical heterocyclic nitrogen compounds which-are applicable in the practice of this invention include the vinyl-substituted pyridines and the vinyl-'sub'sti tutedquinolines. These compounds include the 2 vinyl pyridi'nes such as 2 vinylpyridine; 5-methyl 2-vinyl-pyridine; S-ethyl-Z-Vinylpyridine, also the 5-vinyl-pyridines suchasS-Vinylyridine; 2-methyl-S-vinylpyridine, alsothe divinyl pyridines such as 2,5-divinylpyridine; 3-inethyl 2,5-divinylpyridineu Other'compounds which are also applicable in the practice of this invention include 4- methyl-3-vinylpyridine,= 2-isopropenylpyridine; 5-propy1 2-isopropenylpyridin'e; 2-octyl-5'-vinylpyridine and the vari ous polymerizable quinoline and'isoquin'oline compounds such as 2-vinylquino1ine, S-ethyl-Z-vinylquinoline; 4-heX- yl-5-vinylquinoline; l-vinylisoquinoline; S-methyl-l-isopropenylisoquinoliney 18=divinylisoquinoline; 2,5,8 -trivinylquinoline, 6,7-dimethyl-2t3-divinylquinoline, etc. Generally, and as indicated, any polymerizable, especially vinyl substituted pyridine, quinoline or isoquiuoline is applicable in the practice of this invention.

Other polymerizable heterocyclic nitrogen compounds which can be used in the practice of this invention include the R CH2=(|J substituted (as hereinbefore defined) piperidines (hexahydropyridine) pyrroles, pyrrolidines, especially the vinylsubstituted piperidines, pyrroles, pyrrolidines and-their alkyl derivatives.

, trative of this invention and specific details for operating the present invention are described with comparative resu'lts, showing the improvements obtained by this inven- 1 7 tio'n. However, as indicated, these examples are merely illustrative and not limitiveof this invention.

Example I One - 7 The effectiveness of selenium sulfide asa stabilizer for purposes two similar runs were made using 0.2 percent sulfur in each case, heating one sample in air and the other in an atmosphere of nitrogen. The following results were obtained: 7 l 1 Percent Polym erizatlon Additive 7 Air Nitrogen Selenium mmm fi e V i 3. b3 2. 74 Sulfur 8.14 7.51

Example II Selenium monosulfide (0.3 percent) was added to 2- methyl-5-vinylpyridine and the mixture was heated in an atmosphere of nitrogen for 24hours at a temperature of 200 F. Another sample of 2-methyl-5-vinylpyridine was heated-under the same conditions except that 0.3 percent sulfur was employed as the additive. The following results were obtained Additive; I Percent polymerization Q Selenium monosulfide 2.57 Sulfur 4.31

wherein n is an integer selected from the group consisting of 1 and 2, R is selected from the group consisting of H and CH3, and each R is individually selected from the group consisting of H and alkyl radicals, not more than 12 carbon atoms being present in the total of said R radicals, which comprises adding to said heterocyclic nitrogencompound a polymerization inhibiting amount of a sulfide selected from the group consisting of the sulfides of selenium and tellurium.

2.'Acomposition comprising a heterocyclic nitrogen compound represented by the following structural formula:

wherein n is an integer selected from the group consisting of 1 and 2, R is selected from the group consisting of H and 3 CH3, and each Rf is individually selected from the groupv consisting of H and, alkyl, radicals, not more than ,12carbon .atoms being present in the total of said R-' radicals,-and a polymerization inhibiting amount of a sulfide selected from the group, consisting of the sulfides of selenium and tellurium. l

3. A process for inhibiting the polymerization .of 2- methyl-S-vinylpyridine which comprises adding ,to said compound apolymerization inhibiting amount of, a sub fide selected from the group consisting of the sulfides of selenium and-tellurium. e f

4. A composition comprising 2-viny1pyridine and a poly:

merizationinhibiting amount, of a selenium sulfide.

' 5. A composition comprising 2-methyl-5-vinylpyridine and .a polymerization inhibiting amount of a selenium sulfide. Y I I 6. A composition comprising 2-methyl-5-vinylpyridine and a polymerization inhibiting amount of selenium and between 0.001 and 10% by weight, based onsaid composition, selenium monosulfide.

References Cited in the file of this patent V UNITED STATES PATENTS 1,950,438 Carothers Mar.13,1934 

1. A PROCESS FOR INHIBITING THE POLYMERIZATION OF A HETEROCYCLIC NITROGEN COMPOUND REPRESENTED BY THE FOLLOWING STRUCTURAL FORMULA:
 7. A COMPOSITION COMPRISING 2-VINYLPYRIDINE AND A POLYMERIZATION INHIBITING AMOUNT OF SELENIUM MONOSULFIDE. 